Combustion burners and associated methods of operation

ABSTRACT

This document relates to combustion burners and associated methods of operation. In one aspect a burner is operated to produce harmonic resonance.

TECHNICAL FIELD

This document relates to combustion burners and associated methods of operation.

BACKGROUND

Combustion burners are used in oil and gas applications to heat fluids. Combustion burners are known with spiral nozzles that supply fuel and oxygen to a combustion chamber.

SUMMARY

A method is disclosed comprising operating a burner by combusting a flow of fuel and oxygen within the burner, in which the burner is operated using a set of operating parameters selected to produce and maintain a resonant frequency in a combustion chamber housing of the burner.

A burner is disclosed comprising: a fuel supply line; an oxygen supply line; a combustion chamber housing connected to receive a flow of fuel and oxygen from the fuel supply line and the oxygen supply line; and a controller connected to adjust operating parameters of the fuel supply line, the oxygen supply line, and the burner to operate the burner to produce and maintain a resonant frequency in the combustion chamber housing.

A method is disclosed comprising: supplying a flow of fuel and oxygen to a combustion chamber housing of a burner; and igniting the flow of fuel and oxygen within the combustion chamber housing using an igniter located within a pilot chamber that opens into the combustion chamber housing.

A burner is disclosed comprising: a fuel supply line; an oxygen supply line; a combustion chamber housing connected to receive a flow of fuel and oxygen from the fuel supply line and the oxygen supply line; and an igniter located within a pilot chamber that opens into the combustion chamber housing.

A method is disclosed comprising: combusting a flow of fuel and oxygen within a combustion chamber housing of a burner; and supplying coolant to cool a sidewall and rear wall of the combustion chamber housing.

A burner is disclosed comprising: a fuel supply line; an oxygen supply line; a combustion chamber housing connected to receive a flow of fuel and oxygen from the fuel supply line and the oxygen supply line; and a jacket that wraps around a sidewall and a rear wall of the combustion chamber housing, the jacket defining a coolant channel, which is connected to a coolant inlet and a coolant outlet of the jacket.

A method is disclosed comprising: pumping a supply of oxygen to a burner using an air pump that comprises a variable frequency drive; combining the supply of oxygen with a supply of fuel to create a flow of fuel and oxygen within the burner; combusting the flow of fuel and oxygen within the burner; and controlling the ratio of oxygen to fuel in the flow of fuel and oxygen by adjusting the operation of the air pump with a fuel-oxygen ratio controller.

A burner is disclosed comprising: a fuel supply line; an oxygen supply line; an air pump connected to the oxygen supply line, the air pump comprising a variable frequency drive; a combustion chamber housing connected to receive a flow of fuel and oxygen from the fuel supply line and the oxygen supply line; and a fuel-oxygen ratio controller connected to adjust operating parameters of the fuel supply line, the air pump, and the burner.

A method is disclosed comprising: combining a supply of oxygen and a supply of fuel to produce a flow of fuel and oxygen; and combusting the flow of fuel and oxygen in a burner; in which the supply of oxygen and the supply of fuel are combined with the supply of oxygen having a pressure greater than a pressure of the supply of fuel.

A burner is disclosed comprising: a combustion chamber housing with an open end for exhausting combusted gases; a fuel supply line having a fuel-emitting outlet connected to the combustion chamber housing; an oxygen supply line having an oxygen-emitting outlet connected to the combustion chamber housing; and a fuel-oxygen ratio controller connected to adjust flow on the fuel supply line and the oxygen supply line to maintain the oxygen-emitting outlet at a higher pressure than a pressure at the fuel-emitting outlet.

In various embodiments, there may be included any one or more of the following features: The burner induces the flow of fuel and oxygen into a helical flow within the combustion chamber housing. Supplying fuel, oxygen, or fuel and oxygen through a helical passageway and out a first nozzle into the combustion chamber housing. The first nozzle supplies oxygen to the combustion chamber housing, and a second nozzle supplies fuel to the combustion chamber housing. The first nozzle comprises a plurality of first nozzles; and the helical passageway comprises a plurality of helical passageways located in an annulus that is defined around a fuel passageway to the second nozzle, and each helical nozzle is connected to a respective first nozzle. The helical flow of fuel and oxygen retains a helical flow pattern after combustion and after exiting an open end of the combustion chamber. The combustion chamber housing is cylindrical in shape and exhausts combusted gases out of an open end of the combustion chamber housing. The burner comprises a mixing chamber housing that is: connected to receive and combine a supply of fuel and a supply of oxygen to produce the flow of fuel and oxygen; and connected to supply the flow of fuel and oxygen to the combustion chamber housing through an opening in a rear end, opposite the open end, of the combustion chamber housing. The mixing chamber housing is cylindrical in shape. Supplying coolant to cool a sidewall of the mixing chamber housing. Coolant is supplied to a coolant channel defined within a jacket that wraps around the sidewall of the mixing chamber housing. Supplying coolant to cool a sidewall of the combustion chamber housing. Coolant is supplied to a coolant channel defined within a jacket that wraps around the sidewall of the combustion chamber housing. The jacket wraps around a rear end of the combustion chamber housing opposite an open end of the combustion chamber housing. An initial step of reducing or extending an axial length of the combustion chamber housing to produce and maintain the resonant frequency at the set of operating parameters. Reducing or extending comprising removing or adding, respectively axial sections from or to the combustion chamber housing. The flow of fuel and oxygen resonate at one or both a 2nd harmonic and a 3rd harmonic. The flow of fuel and oxygen resonate at one or both a 4^(th) harmonic and a 5th harmonic. Oxygen comprises air. During operation, controlling the ratio of air to fuel in the flow of fuel and oxygen by adjusting a supply of air and a supply of fuel with a fuel-air ratio controller, in which the supply of air and the supply of fuel are combined to produce the flow of fuel and oxygen. The ratio of air to fuel is maintained in the flow of fuel at between 11:1 and 16:1. The ratio of air to fuel is maintained in the flow of fuel and oxygen at 12.6 to 14.5. The ratio of air to fuel is maintained in the flow of fuel and oxygen at about 13:1. During operation, the ratio of air to fuel is controlled to produce 3-12%, for example 4-7%, 02 in exhaust expelled from the burner. During operation, the ratio of air to fuel is controlled to produce about 6% O2 in exhaust expelled from the burner. The supply of air passes through an air pump that comprises a variable frequency drive. Controlling comprises: measuring an output temperature of a) exhaust gas from the burner or b) a medium that is positioned to be heated by exhaust gas expelled from the burner; adjusting the flow of the supply of air through an air pump based on the output temperature; measuring a flow characteristic of the supply of air at an output of or downstream of the air pump; and adjusting the flow of the supply of fuel in response to the measured flow characteristic of the supply of air. The flow of the supply of air is adjusted up or down when the output temperature is below or above, respectively, a predetermined operating range. The supply of air and the supply of fuel are combined with the supply of air having a higher pressure than the supply of fuel. The supply of air and the supply of fuel are combined with: the supply of air having a pressure of greater than zero and below fifty psi; and the supply of fuel having a pressure of greater than zero and below twenty psi. The supply of air and the supply of fuel are combined with: the supply of air having a pressure of between nine and fifteen psi; and the supply of fuel having a pressure of between one and ten psi. The fuel comprises natural gas. Combustion of the flow of fuel and oxygen occurs within combustion chamber housing. The flow of fuel and oxygen are supplied to the combustion chamber housing via a nozzle with a diameter of greater than zero inches and less than or equal to fifteen inches; and a length of the combustion chamber housing is greater than zero and less than or equal to fifty inches. A ratio of: a nozzle through which the flow of fuel and oxygen are supplied to the combustion chamber housing; and an axial length of the combustion chamber housing; is 5-20:1. An axial length of the combustion chamber housing is between eight and fifty inches. The burner comprises an igniter within a pilot chamber that opens into the combustion chamber housing. The pilot chamber opens into a rear wall of the combustion chamber housing. The igniter comprises one or more of a spark plug, a glow plug, flame rod, or a pilot light. Supplying pilot fuel and oxygen to the pilot chamber; igniting the pilot fuel and oxygen within the pilot chamber; and pumping ignited gases from the pilot chamber into the combustion chamber housing. Monitoring combustion via a combustion sensor associated with a sight glass connected to the combustion chamber housing. The sight glass is on a rear wall of the combustion chamber housing. The combustion sensor comprises an ultraviolet light sensor. The sight glass comprises quartz. The combustion sensor is located within a sensor chamber that connects to the sight glass. Exhaust gases exit the burner, via an open end of the combustion chamber housing, travelling at a velocity at or above one hundred fifty feet per second. Exhaust gases that exit the burner have one or more of the following characteristics: zero or nominal carbon monoxide; nominal NOx; and 100% combustion efficiency. A supply of fuel and a supply of oxygen are connected via a first nozzle and a second nozzle, respectively, at a mixing point within the burner to produce the flow of fuel and oxygen; and a ratio of cross-sectional area of the first nozzle and the second nozzle is at or greater than 1:1. The ratio of cross-sectional area of the first nozzle and the second nozzle is at or greater than 3:1. T the ratio of cross-sectional area of the first nozzle and the second nozzle is 1-4:1. The burner is connected to exhaust combusted gases through a fire tube of a heat exchanger. The burner is connected to provide heat to one or more of a frac water pond, a boiler, a power generator, a ground heater, a glycol vessel, a line heater, a gas dehydrator, and an oil and gas separator treater. The burner is located at an oil and gas production or processing facility.

These and other aspects of the device and method are set out in the claims, which are incorporated here by reference.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments will now be described with reference to the Figures, in which like reference characters denote like elements, by way of example, and in which:

FIG. 1 is a side view of a burner test apparatus.

FIG. 2 is a perspective view of the burner test apparatus of FIG. 1.

FIG. 3 is an end view of the burner test apparatus of FIG. 1.

FIG. 4 is a top plan view of a fire tube with a burner mounted to one end of the fire tube.

FIG. 5 is a perspective view of a burner.

FIG. 6 is an exploded view of the burner of FIG. 5.

FIG. 7 is an end view of the combustion end of the burner of FIG. 5.

FIG. 8 is a section view taken along the 8-8 section lines from FIG. 7.

FIG. 8A is a schematic view of a control methodology for operating the burner of FIG. 5 with a fuel-air ratio controller.

FIG. 8B is a section view taken along the central axis of the fuel nozzle into the mixing chamber.

FIG. 9 is a section view taken along the 9-9 section lines from FIG. 7.

FIG. 9A is an exploded view of the area delineated by dashed lines in FIG. 9.

FIG. 10 is a perspective view of the rear housing part of the burner of FIG. 5.

FIG. 11 is an end view of another embodiment of a rear housing part.

FIGS. 12-27 are graphs of test results from various burners within the scope disclosed here.

DETAILED DESCRIPTION

Immaterial modifications may be made to the embodiments described here without departing from what is covered by the claims.

Referring to FIGS. 2-9, a burner according to the present disclosure, as indicated by general reference numeral 10, is shown. Referring to FIG. 8, the illustrated embodiment of the burner 10 may comprise a main body 10A comprising a rear housing 56, a central housing 54, a front housing 50, an air supply such as an air conveying passageway 100 and a fuel supply such as a fuel conveying passageway 112. The burner 10 may form an internal mixed fluids chamber 126 having a narrower rearward mixing chamber 40 and a relatively wider forward combustion chamber housing 34. The main body 10A generally houses the parts, and/or components, and/or elements of the present disclosure. The burner 10 may be operated by combusting a flow of fuel and oxygen within a combustion chamber housing 34 of the burner 10.

Referring to FIG. 8, the main body 10A may have a rear end 128 and a front end 130, an outlet nozzle area 132 disposed immediately forwardly of the front end 130, and may define a longitudinal axis 182 extending between the front end 130 and the rear end 128. It should be understood that although for some shapes of burner systems the determination of front end and the rear end might be somewhat arbitrary, the front end may generally be defined as where the flame is exhausted, and the rear end is defined as the area where the air and the fuel have their inputs, and where the mixing of the air and the fuel possibly begins.

It should be understood that for the sake of convenience, the term oxygen may be used to describe ambient air, or air from a pressurized or compressed source of air. In some cases oxygen is from a pressurized or compressed source of oxygen. If a source of air is used, the oxygen in the air may be reacted with a fuel such as propane, natural gas, syngas, diesel, and so on. It is also contemplated that hydrogen could be used along with the oxygen. In some cases liquid fuel is used, for example liquid diesel. The liquid fuel may be mixed with the oxygen while the liquid fuel is in a liquid state or after being converted to a gas state or atomized into a gas-like state.

Referring to FIG. 8, the burner 10 may define an air supply or air conveying passageway 100. In the illustrated embodiment, the air conveying passageway 100 may have, in seriatim and in fluid communication one with the next, a first air-receiving inlet 120A, an intake air-flow chamber 102, at least one air-flow opening 124, a turbulent air-flow chamber 104, an air-flow channel 116, and a first nozzle such as air-emitting outlet 108 into a mixing chamber 40. Referring to FIG. 10, the at least one air-flow opening 124 may comprise one or more air flow openings, such as a first air-flow opening 124A, a second air-flow opening 124B, a third air-flow opening 124C, and a fourth air-flow opening 124D. Referring to FIGS. 8 and 10, burner 10, for example rear housing 56, may form an air-flow disruption apparatus 168 disposed in operative relation in conjunction with the air-flow passageway 100 (FIG. 8), to thereby create a turbulent flow of air in the air flow passageway 100 (FIG. 8). The air-flow disruption apparatus 168 may comprise in seriatim and in fluid communication one with the next, the first air flow inlet 120, a substantially annular intake air flow chamber 102, an air flow opening 124, a substantially annular turbulent air flow chamber 104, and an air transfer egress 170.

Referring to FIG. 8, there may be at least one air-receiving inlet 120 in the main body 10A, and in the illustrated embodiment, there may be a first air-receiving inlet 120A and a second air-receiving inlet 120B in the main body 10A, specifically in the rear housing 56 of the main body 10A, provided in order to generally balance the air flow introduced into the intake air-flow chamber 102. The second air-receiving inlet 120B is similar to the first air-receiving inlet 120A in that it is in seriatim and in fluid communication with the intake air-flow chamber 102, the first air-flow opening 124A, the turbulent air-flow chamber 104, the first air-flow channel 116A, and the air-emitting outlet 108, in the same manner as described above for the first air-receiving inlet 120A.

Referring to FIGS. 10 and 11, the first air-receiving inlet 120A and the second air-receiving inlet 120B may each be disposed at the rear end 128 of the burner 10. The first air-receiving inlet 120A and the second air-receiving inlet 120B may be angularly spaced one hundred eighty degrees (180) apart around the longitudinal axis 182, in order to effectively maximize the subsequent mixing of air flow. Other configurations and numbers of inlets may be used. The first air-receiving inlet 120A and the second air-receiving inlet 120B may each be oriented generally along the longitudinal axis 182, as shown, but could alternatively be oriented at another angle. There may also be additional air-receiving inlets appropriately located in the main body 10A to accommodate the need for additional air input. It should also be noted that in an alternative embodiment, it is contemplated that there could be additional inlets for introducing a secondary type of fuel into the supply of air, such as hydrogen and even including the un-burnt emissions from other types of burner systems, and the like.

Referring to FIG. 10, there may be a chamber-separating structure 106 that in the illustrated embodiment comprises a perforated metal wall that is substantially annular in shape. As illustrated, the chamber-separating structure 106 may be a unitary wall that is substantially annular. The wall 106 may act as a chamber-separating structure that separates the intake air-flow chamber 102 and the turbulent air-flow chamber 104, and that separates the intake air-flow chamber 102 and the turbulent air-flow chamber 104 one from the other, and defines the first air-flow opening 124A, the second air-flow opening 124B, the third air-flow opening 124C, and the fourth air-flow opening 124D. The first air-flow opening 124A, the second air-flow opening 124B, the third air-flow opening 124C and the fourth air-flow opening 124D are disposed in substantially equally spaced relation around the substantially annular wall 106. Referring to FIG. 10, the intake air-flow chamber 102 may be substantially annular and the turbulent air-flow chamber 104 may be substantially annular, and the intake air-flow chamber 102 is disposed in surrounding relation around the turbulent air-flow chamber 104. The intake air-flow chamber 102 and the turbulent air-flow chamber 104 are substantially concentric with each other.

Referring to FIGS. 8 and 10, burner 10 may have the first air-flow opening 124A, the second air-flow opening 124B, the third air-flow opening 124C, and the fourth air-flow opening 124D. Each of the first air-flow opening 124A, second air-flow opening 124B, the third air-flow opening 124C, and the fourth air-flow opening 124D may be similar in nature one to the other in that each is in seriatim and in fluid communication with the first air-receiving inlet 120A, the intake air-flow chamber 102, the turbulent air-flow chamber 104, the air-flow channel 116 (FIG. 8), and the air-emitting outlet 108 (FIG. 8), in the same manner as described above for the first air-flow opening 124A.

Referring to FIG. 8, a supply of air, such as a source of air flow 136 may be connected in fluid communication to the air-receiving inlet 120 of the air conveying passageway 100. In some cases, the source of air flow 136 may be connected to the first air-receiving inlet 120A via a first connecting hose 136A and may be connected to the second air-receiving inlet 120B via a second connecting hose 136B. It should be noted that in the illustrated embodiment, the source of air flow 136 is the only source of air flow. Alternatively, the source of air flow 136 may be the primary source of air flow along with a secondary source of air flow at a suitable pressure. Referring to FIG. 7 and Tables 7 and 8, example cross-sectional areas of outlets 108 are illustrated.

Referring to FIG. 8, the main body 10A may have a supply of fuel, such as a fuel nozzle-receiving passageway 134. Passageway 134 may be generally centrally disposed in the burner 10 and may be oriented along longitudinal axis 182. Referring to FIG. 8, the fuel conveying passageway 112 may extend through the substantially annular intake air-flow chamber 102 and the substantially annular turbulent air-flow chamber 104. The fuel conveying passageway 112 may have in seriatim and in fluid communication one with the next, a fuel-receiving inlet 110, a main passageway 138, and a second nozzle or fuel-emitting outlet 114 for delivering fuel to the outlet area 132 of the burner 10, by passing a flow of fuel from the fuel-receiving inlet 110 through the main passageway 138 to the fuel-emitting outlet 114. In the illustrated embodiment, the fuel conveying passageway 112 may be disposed within a substantially straight fuel nozzle 80 that resides within the fuel nozzle-receiving passageway 134.

Referring to FIG. 8, the fuel conveying passageway 112 may extend from its fuel flow inlet 110 at the rear end 80B of the fuel nozzle 80 to the fuel flow outlet 114 at the front end 80A of the fuel nozzle 80, and may be substantially straight except for the forward portion 84 at the front end 80A of the fuel nozzle 80 where the fuel conveying passageway 112 may furcate into two or more passageways, such as six separate passageways 112A, 112B, 112C, 112D, 112E, 112F each having its own respective second nozzles such as fuel flow outlet 114A, 114B, 114C, 114D, 114E, 114F.

Referring to FIG. 7, the second nozzle such as fuel-emitting outlet 114 may comprise two or more outlets, such as a first fuel-emitting outlet 114A, a second fuel-emitting outlet 114B, a third fuel-emitting outlet 114C, a fourth fuel-emitting outlet 114D, a fifth fuel-emitting outlet 114E, and a sixth fuel-emitting outlet 114F. The first fuel-emitting outlet 114A, the second fuel-emitting outlet 114B, the third fuel-emitting outlet 114C, the fourth fuel-emitting outlet 114D, the fifth fuel-emitting outlet 114E, and the sixth fuel-emitting outlet 114F may each be oriented at an angle of about eleven degrees with respect to the longitudinal axis 182. Other suitable angles greater or smaller may be used. Any other suitable angle may alternatively be used. Referring to FIG. 8B and Table 9 below, example cross-sectional areas of outlets 114 and passageways 112 are illustrated for different sizes of burners 10.

Referring to Tables 7-10, a suitable ratio of cross-sectional area of the first nozzle and the second nozzle may be used, such as a ratio that is at or greater than 1:1. The ratio of cross-sectional area of the first nozzle and the second nozzle may at or greater than 3:1. The ratio of cross-sectional area of the first nozzle and the second nozzle may be 1-4:1. The larger the ratio, the less resistance to air flow, which may be advantageous particularly when using a stoichiometric excess of oxygen.

Referring to FIG. 8, a source of gaseous fuel flow 140 may be connected in fuel delivery relation to the fuel flow inlet 110 of the fuel conveying passageway 112 via a connecting hose 140A. It should be noted that in the illustrated embodiment, the source of gaseous fuel flow 140A is the only source of fuel flow. Alternatively, the source of fuel flow could be the primary source of fuel flow along with a secondary source of fuel flow at a suitable pressure.

Referring to FIG. 8, the fuel nozzle 80 may comprise an external rear portion 80C disposed at the rear end 80B of the fuel nozzle 80. The external rear portion 80C may project rearwardly from the rear end 128 of the main body 10A. The external rear portion 80C of the fuel nozzle 80 may be threaded to accept a co-operating nut 66 thereon, to thereby retain the fuel nozzle 80 in place in the main body 10A.

Referring to FIG. 8, a portion of the air conveying passageway 100 may be disposed rearwardly of the combustion chamber housing 34. Passageway 100 may comprise a suitable number of air flow channels, such as an air flow channel 116 disposed radially outward of the fuel nozzle 80. Channel 116 may comprises two or more, for example five substantially parallel air flow channels each disposed on the fuel nozzle 80, namely a first air flow channel 116A, a second air flow channel 116B, a third air flow channel 116C, a fourth air flow channel 116D, and a fifth air flow channel 116E. The first, second, third, fourth, and fifth air flow channels 116A-E are in fluid communication and in seriatim with the air flow inlet 120, the intake air flow chamber 102, the first air flow opening 124A, and the turbulent air flow chamber 104.

Referring to FIG. 7, the air flow channels may terminate at respective first nozzles, such as respective air flow outlets. For example the first air flow channel 116A, the second air flow channel 116B, the third air flow channel 116C, the fourth air flow channel 116D, and the fifth air flow channel 116E may terminate in a first air flow outlet 108A, a second air flow outlet 108B, a third air flow outlet 108C, a fourth air flow outlet 108D, and a fifth air flow outlet 108E, respectively, which together form the overall air flow outlet 108. It has been found that it is to have a plurality of air-flow channels for the purpose of even air flow and distribution. Any suitable number of air-flow channels could be used depending on the specific application of the burner 10, the size of the burner 10 and the fuel nozzle 80, and so on. Various fuel nozzles according to the present disclosure have been tried, including from two air-flow channels on up.

Referring to FIG. 8, the burner 10 may induce a helical flow of fuel and oxygen within at least a portion of the internal mixed fluids chamber 126, for example within the combustion chamber housing 34. The burner 10 may supply, fuel, oxygen (shown), or fuel and oxygen through a helical passageway or passageways, such as air-flow channels 116, and out a first nozzle or nozzles, for example air-emitting outlets 108, into the combustion chamber housing 34. The first nozzle may supply oxygen to the combustion chamber housing 34, and a second nozzle, for example a second nozzle or nozzles, such as fuel-emitting outlets 114, may supply fuel to the combustion chamber housing 34. The helical passageway may comprise a plurality of helical passageways or channels 116 located in an annulus 188 that is defined about a fuel passageway 112 to the outlets 114. The burner 10 may induce a helical flow of fluids that retains a helical flow pattern after exiting an open end 148 of the internal mixed fluids chamber 126, for example that retains helical flow one or more of five, ten, twenty, fifty, or one hundred feet past the burner 10. In some cases a continual helical exit flow may be detected by a uniform temperature around a circumference of a fire tube into which exhaust gases are expelled, as with purely axial flow convection would be expected to cause a higher temperature at a top portion of the fire tube. Referring to FIGS. 6, 7, and 8, each of the first, second, third, fourth and fifth air-flow channels 116A, 116B, 116C, 116D, 116E may have a respective air flow outlet 108A-E disposed adjacent the fuel-emitting outlet 114 for delivering air to the air-and-fuel mixing chamber 40 of the burner 10.

Referring to FIGS. 7-8, respective axes of each of the plurality of helically shaped air-flow channels 116 may be substantially parallel to respective axes of adjacent helically shaped air-flow channels 116 when viewed in cross-section to axis 182. The helically shaped air-flow channels 116 may be disposed about the exterior of the fuel nozzle 80.

Referring to FIGS. 6 and 8, the internal mixed fluids chamber 126, such as one or both of housing 34 and chamber 40, may be elongate and substantially cylindrical in shape, and may define a generally central longitudinal axis 182. Chamber 126 may extend between a rear end 126B and an open end/heat producing front end 126A, may define a mixing chamber 40, with a rear end 40B and a front end 40A, and may define a relatively wider forward combustion chamber housing 34 with a rear end 34B and a front end 34A. The internal mixed fluids chamber 126 may exhaust combusted gas out an open end or a heat producing front end 126A.

Referring to FIG. 8 the mixing chamber 40 may be connected such that the destination for subsequent combustion is at or adjacent a nozzle, into the combustion chamber housing 34, such as outlet area 132, and is disposed within the internal chamber 126. The front end 34A of the combustion chamber housing 34 may be disposed at the opposite to the main body 10A. The mixing chamber housing 40 may be connected to receive and combine a supply of fuel and a supply of oxygen and may be connected to supply fuel and oxygen to an opening in an end plate, which may define rear end 34B, at a closed end opposite the open end 34A of, the combustion chamber housing 34. The mixing chamber housing 40 may be cylindrical in shape. The combustion chamber housing 34 may be cylindrical in shape.

The burner 10 may be operated using a set of operating parameters selected to produce and maintain a resonant frequency in the combustion chamber housing 34. A resonant frequency may be a standing wave pattern for an air column, with vibrational antinodes present at any open end and vibrational nodes present at any closed end. The resonant frequency vibration may operate under similar principles as that of a pipe organ. The burner 10 may be configured and/or operated to produce one or more of the 1st, 2nd, 3rd, 4th, or 5th harmonic or other suitable harmonic of the combustion chamber housing 34. The sound produced via resonance oscillation may be produced by pressure waves generated from a vibrational source, such as the combustion process itself. It is not known why a combustion flame produces oscillations, but one theory is that the combustion process, though seemingly continuous, actually occurs in a set of discrete and repeated stages of ignition. The resonant frequency may be produced and maintained via another suitable method, such as a vibrating pad at a rear end of the housing 34. Operating a burner at a resonant frequency is a step in the opposite direction of the state of the art, which teaches one to avoid combustion screech using dampers, various operating parameters, and other devices and methods. However, in some cases resonant frequency operation has been found to improve burner performance. In some cases, during operation with a fire tube, the lower sensor is hotter than the top sensor at several positions, with a delta of about 100 C.

Resonant frequency oscillation may be understood by examining the operation of a pipe organ. The pipe organ is a musical instrument that produces sound by driving pressurized air (called wind) through organ pipes selected via a keyboard. The organ's continuous supply of wind allows it to sustain notes for as long as the corresponding keys are depressed, unlike the plano and harpsichord whose sound begins to dissipate immediately after it is played. Most organs, both new and historic, have electric blowers, although others can still be operated manually. The wind supplied is stored in one or more regulators to maintain a constant pressure in the windchests until the action allows it to flow into the pipes.

Natural frequency is the frequency at which a system tends to oscillate in the absence of any driving or damping force. Free vibrations of an elastic body are called natural vibrations and occur at a frequency called the natural frequency. Natural vibrations are different from forced vibrations which happen at frequency of applied force (forced frequency). If forced frequency is equal to the natural frequency, the amplitude of vibration increases manyfold. This phenomenon is known as resonance. In physics, resonance is a phenomenon in which a vibrating system or external force drives another system to oscillate with greater amplitude at a specific preferential frequency. Frequencies at which the response amplitude is a relative maximum are known as the system's resonant frequencies or resonance frequencies. At resonant frequencies, small periodic driving forces have the ability to produce large amplitude oscillations. This is because the system stores vibrational energy.

The lowest resonant frequency of a vibrating object is called its fundamental frequency. Most vibrating objects have more than one resonant frequency and those used in musical instruments typically vibrate at harmonics of the fundamental. A harmonic is defined as an integer (whole number) multiple of the fundamental frequency. Vibrating strings, open cylindrical air columns, and conical air columns will vibrate at all harmonics of the fundamental.

Referring to FIG. 6, an axial length 184 of the combustion chamber housing 34 may be tailored, for example by reducing or extending an axial length 184 of the housing 34, to produce and maintain the resonant frequency at the set of operating parameters. Reducing or extending may be accomplished by removing or adding, respectively, axial segments, for example two-inch ring segments forming an outer sidewall of the housing 34. Axial segments may be added via welding. Axial length 184 will determine the natural frequencies of the burner 10, with longer axial lengths resulting in relatively lower natural frequencies, and shorter lengths resulting relatively higher natural frequencies. Tailoring other variables can affect natural frequency as well, such as increasing or decreasing the diameter of the combustion chamber housing to decrease or increase, respectively, the natural frequencies of the housing. Tailoring combustion chamber housing 34 may be carried out in tandem with test runs of the burner 10 a set of operating parameters, with a run being completed at a particular axial length, the frequency and intensity of sound produced being measured, the axial length of the housing 34 being adjusted, and a subsequent test run being carried out, with subsequent measurements of sound produced, until resonance is achieved and optimized. Combustion chamber 126 may comprise telescopic parts, which may be adjusted to optimize and produce a resonant frequency during operation. Referring to FIG. 6, axial length 184 of combustion chamber housing 34 may be adjusted by moving the telescopic parts closer to one another to decrease the axial length 184, or by moving the telescopic parts farther from one another to increase axial length 184. Production of the resonant frequency and associated harmonics of the burner 10 may decrease temperature differences or increase uniformity of heat distribution between points along longitudinal axis of the internal chamber 126. Longer axial lengths may produce higher order harmonics and relatively higher exhaust gas velocity. Thus, tailoring may include tailoring to produce a first harmonic, then tailoring to produce a second or third harmonic, and so on, by adding axial length to the combustion chamber housing. The increase in exhaust velocity may increase the effective range of the burner. For example in tests performed, at the second harmonic wind flow could be felt twenty feet downstream of the burner in open air, while at the third harmonic, wind flow could be felt at fifty feet.

Referring to FIG. 6, the flow of fuel and oxygen may be supplied to combustion chamber housing 34 via a nozzle, for example defining the outlet area 132, having a diameter of greater than zero inches and less than or equal to fifteen inches. A length of the combustion chamber housing 34, for example axial length 184, may be greater than zero and less than or equal to fifty inches. A ratio of the nozzle through which the flow of fuel and oxygen are supplied to the combustion chamber housing 34 and an axial length of the combustion chamber housing 34 may be 5-20:1 or other suitable ratios. An axial length of the combustion chamber housing 34 may be between eight and thirty, fifty, or more inches. Referring to Table 11 below, example dimensions, including axial lengths, are illustrated for the combustion chamber housings 34 of different sizes of burners 10.

Referring to FIG. 6, various parameters in the set of operating parameters may be adjusted to produce and maintain a resonant frequency in the housing 34. Any one or more of the following may be considered parameters: a diameter of the combustion chamber housing 34, the degree of cooling of combustion chamber housing 34 via coolant channels, a pitch of vanes or threading of nozzle 80, cross-sectional area of fuel or air emitting outlets, flow rate, for example air flow rate, gas flow rate, or both air and gas flow rate, and others, including ratios of variables, such as the ratio of air to fuel or air pressure to fuel pressure.

Referring to FIGS. 6, 9, and 9A, burner 10 may comprise an igniter 70 within a pilot chamber 71 that opens, for example via a port 77A, into the combustion chamber housing 34. The pilot chamber may be formed by a pilot housing 74. Pilot housing 74 may have connected to it a pilot nozzle 76 and/or a pilot housing cap 46. Igniter 70 may be mounted to a rear end 34B of housing 34. The pilot chamber may open into a rear wall 62 of the combustion chamber housing 34. Referring to FIG. 8, in some cases, such as with burners 10 with mixing chamber nozzles of two or less inches in diameter, the pilot chamber opens near a front end 34A of the combustion chamber housing 34. The igniter 70 may comprise one or more of a spark plug, a glow plug, flame rod, or a pilot light. The igniter 70 may be mounted on a support structure 72. Referring to FIGS. 7 and 9A, fuel and oxygen may be supplied, for example via separate inlets 79 and 73, to pilot chamber 71 and ignited within the pilot chamber. Ignited gases from the pilot chamber may be pumped, for example using an air pump (not shown) into the combustion chamber housing 34. A junction box 48 may connect to spark house cap 48 to complete the igniter 70. A coupler 81 may connect the nozzle 76 to the housing 34. Other suitable pilot ignition systems may be used, such as a flame rod that extends within housing 34, although in some cases such a system has been found to be problematic, particularly where vibration, turbulence, and extreme heat, caused by operation in the burner causes the flame rod to migrate toward a sidewall of the housing 34, potentially leading to false no-flame readings.

Referring to FIGS. 6 and 9A, combustion may be monitored via a combustion sensor 52. Sensor 52 may be associated with a sight glass 82, which may fit into a coupler 78, and may mount one or more quartz lenses 83, connected to the combustion chamber housing 34. Sight glass 82 may be inset within a rear wall 62 of the combustion chamber housing 34. The combustion sensor 52 may comprise an ultraviolet light sensor, with applicable leads 92 that connect to a controller for monitoring operation of the burner 10. Sight glass 82, for example lens 83, may comprise quartz. The combustion sensor 52 may be located within a sensor chamber that connects to the sight glass 82. An ultraviolet sensor is able to detect the presence of radiation indicative of burner operation. Other suitable sensors may be used.

The pilot and combustion sensor systems may each communicate with the combustion chamber housing via a ½″ port (such as ports 77A and 77B) in the back of the combustion chambers. One port provides UV flame detection and the other provides for a flame to ignite the main burner. Although the flame is a pilot, it may in some cases be considered a direct fire system that lights the pilot and the main flame directly after. With burners whose mixing chamber nozzle is less than 3″ a pilot may be used that sits at the open end of the combustion chamber and requires proof of flame for several seconds before the main burner gas is turned on.

Referring to FIG. 8, exhaust gases may exit the burner 10, via an open end 148 of the combustion chamber housing 34, for example travelling at a velocity at or above one hundred fifty feet per second. Exhaust gases that exit the burner 10 may have one or more of zero or nominal carbon monoxide, nominal NOx, and 100% combustion efficiency. In some cases NOx levels may be 50 ppm, 30 ppm, or lower. In some cases, the achievement of a higher level of harmonic may achieve a higher output velocity in expelled exhaust gases. For example, in some cases the 2^(nd) harmonic achieves ˜20 ft/sec, the 3rd gets 150 ft/sec, and so on.

A burner that is extremely efficient and produces an extreme amount of heat may require cooling. It has been found that with an extremely efficient burner, the extreme heat produced by the burner tends to increase the nitrous oxide (NOx) levels that are output by the burner. NOx is a generic term for mono-nitrogen oxides (NO and NO2). These oxides are produced by reaction of fuel with atmospheric nitrogen, and/or residual nitrogen in the fuel, during combustion, especially combustion at high temperatures. An increase in nitrous oxide (NOx) levels is highly undesirable for various reasons. Most, or possibly all, fuels that are used in burners contain in their natural state the constituents that can produce emissions such as NOx. Upon these fuels being ignited, the NOx and other emissions are released. When the materials (such as carbon steel, stainless steel, and so on) that make up the combustion chamber housing 34 come into direct contact with the ignited fuels of the burner, such materials can reach temperatures of near failure or exceed their predetermined failure point. When such temperatures are reached, the materials can cause additional NOx to be created during combustion.

Referring to FIG. 6, coolant may be supplied to cool a cylindrical side wall 34G, and hence an interior sidewall 126C of the combustion chamber housing 34. The jacket 34C may form a heat transfer apparatus and/or heat recovery apparatus, for example a combustion chamber cooling jacket, the jacket 34C having a front end 34D and a rear end 34E with longitudinal axis 182 extending between the front end 34D and the rear end 34E when assembled. The combustion chamber coolant jacket 34C may be elongate and may have a length 184 defined between the front end 34D and the rear end 34E. The jacket 34C may be structured to wrap around, for example encircle and cover the entirety of, sidewall 126C of the combustion chamber housing 34. The combustion chamber coolant jacket 34C may define a fluid receiving and circulating chamber 122 housing a series of dividers or vanes 97 that collectively define a serpentine coolant channel 190, forcing fluid entering the chamber 122 via an inlet port 38A in jacket 34C to circumferentially crisscross over the external surface area of sidewall 126C, travelling in a direction 186 defined by channel 190, exiting via port 38B in jacket 34C.

Referring to FIG. 6, in some cases, jacket 34C wraps over a rear end, for example end 34B of the combustion chamber housing 34C. In one such case, a rear portion of jacket 34C is formed by lid plate 62, which defines a fluid circulating chamber 122A therebetween. Vanes 98 may be positioned to define a coolant channel 190A that extends from an inlet slot 99A to an outlet slot 99B in inner cylinder 68 of the housing 34. In the example shown, coolant supplied via inlet 38A splits and travels simultaneously through channels 190 and 190A, returning via slot 99B and outlet 38B. Cooling the rear end 34B of housing 34 may improve the longevity of the burner 10 and may provide safer, more reliable burner operation.

Coolant may be supplied to cool a side wall 50C of the front housing 50 or mixing chamber 40. For example, a mixing chamber jacket 40C may wrap around a sidewall of mixing chamber 40, and may be located having a front end 40D and a rear end 40E coterminous with front end 40A and rear end 40B of housing 40. A plurality of rear fluid directing plates or vanes 50A and 50B may be disposed in the rear fluid receiving and circulating chamber 194 of the jacket 40C. Coolant may be circulated through a coolant channel 192 defined by vanes 50A and 50B. Coolant may enter chamber 194 via an inlet 42, circulate through channel 192, and exit via an outlet 44. Combustion may occur in mixing chamber 40, and residual heat from combustion within housing 34 may naturally migrate into mixing chamber 40, and hence it may be advantageous to cool the mixing chamber 40.

The fluid receiving and circulating chamber 122 may circulate a cooling fluid therein (not shown), such as water, or glycol, or any other suitable cooling fluid. In some cases combustible oil based coolant or any other type of combustible coolant may be avoided. Alternatively, a non-combustible cooling fluid in its gaseous state may be used. Referring to FIG. 6, a suitable supply hose and return hose (not shown) may be connected to inlet 38A and outlet 38B, respectively. In some cases, the supply and return hoses may be connected to a common source of fluid, such as a coolant tank. Heat may be recovered from the heated fluid either directly from the source of cooling fluid (not shown), or from a heat exchanger or the like, as the cooling fluid circulates. The heat from the cooling fluid may be used to preheat the fuel being supplied to the burner 10, if appropriate and desired.

Referring to FIG. 6, in an embodiment, the jacket 34C may comprise a substantially cylindrical outer wall 34F generally surrounding a substantially cylindrical inner wall 34G. The substantially cylindrical outer wall 34F and the substantially cylindrical inner wall 34G may together define the fluid receiving and retaining chamber 122 therebetween. The substantially cylindrical outer wall 34F and the substantially cylindrical inner wall 34G may be retained in spaced relation by a front end wall 34H and a rear end wall 34I. The substantially cylindrical outer wall 34F may be press fit, or fit via another suitable method such as welding, into place over the front end wall 34H and a rear end wall 34I. The substantially cylindrical outer wall 34F, the substantially cylindrical inner wall 34G, the front end wall 34H and the rear end wall 34I may together define the fluid receiving and retaining chamber 122 therebetween. The substantially cylindrical inner wall 34G may define the burner passageway 180.

Jacket 34C, rear jacket plate 98, and/or jacket 40C may lower NOx emissions from burner 10, for example by lowering an operating temperature of combustion chamber housing 34 and/or mixing chamber housing 40. Without cooling, the operating temperature of combustion chamber housing 34 and/or mixing chamber housing 40 may rise to 3750 degrees Fahrenheit or beyond, and may melt or damage burner 10. Cooling the mixing chamber 40, the housing 34, and the rear end wall of the housing 34 may reduce or avoid thermal shock of the combustion chamber, also may also reduce the chance of accidental burns caused by a user touching an exterior surface of the burner 10.

Referring to FIG. 8 after a significant amount of experimentation over a considerable amount of time, it has unexpectedly been found that some of the burners 10 disclosed here operate with complete combustion including nominal NOx emissions, using a source of gaseous fuel flow that delivers fuel to the fuel flow inlet 110 of the fuel conveying passageway 112 at a relatively low gauge pressure, and a source of air flow 136 that delivers air to the air flow inlet 120 of the air conveying passageway 100 at a relatively low gauge pressure. Further, it has unexpectedly been found that in some cases complete combustion including no discernable or measureable CO emissions, may be achieved using a source of air flow 136 that delivers air to the air flow inlet 120 of the air conveying passageway 100 at a gauge pressure higher than the pressure at which the source of gaseous fuel flow 140 delivers fuel to the fuel flow inlet 110 of the fuel conveying passageway 112.

Referring to FIGS. 2-9, it has been found that numerous relationships between the parameters of various portions, segments, parts, components, and the like of the burner 10, such as the various sizes and ratios of sizes of the various portions, segments, parts, components, and the like of the burner 10, may be significant as related to the optimized operation of the burner 10. It has also been found that it may be useful to have the predetermined parameters of the burner 10 are within ranges of ratios one with respect to another. In some cases the combustion and flame may be contained entirely within the combustion chamber housing 34, so that only heated exhaust gases are expelled from the burner.

Referring to FIG. 8A, during operation, a fuel-air ratio controller may be used to adjust and optimize operation of the burner 10. The ratio of air or oxygen to fuel in the flow of fuel and oxygen may be controlled by adjusting a supply of air and a supply of fuel with fuel-air ratio controller 141, in which the supply of air and the supply of fuel are combined to produce the flow of fuel and oxygen within the burner 10. The ratio of air to fuel may be maintained in the flow of fuel at between 11:1 and 16:1 or another suitable ratio. Ratios of air to fuel refer to a ratio of standard cubic feet of air per standard cubic feet of fuel. The ratio of air to fuel may be maintained in the flow of fuel and oxygen at 12.6 to 14.5:1. The ratio of air to fuel may be maintained in the flow of fuel and oxygen at about 13:1. An excess of oxygen may provide enough extra oxygen above a stoichiometric ratio to cool the flame to reduce the thermally produced NOx without extinguishing the combustion.

Referring to FIGS. 8A and 4, an output temperature may be measured of either a) exhaust gas from the burner 10 or b) a medium 199 (FIG. 4) such as water in a frac water pond in which a fire tube 197 or other heat exchanger is positioned, that is positioned to be heated by exhaust gas from the burner 10 may be measured. Referring to FIG. 8A, the flow of the supply of air through the air pump 143 may be adjusted by controller 141 based on the output temperature, which may be sensed via sensor 151. The flow of the supply of air may also be adjusted using readings from other sensors, such as O2 sensor 149 in an exhaust stream from the burner 10. A flow characteristic of the supply of air at an output of or downstream of the air pump 143 may be measured, for example using flow or pressure sensor 147 downstream of pump 143. Flow adjustments for the supply of oxygen may be made by adjusting settings on the variable frequency drive 145, and in addition to or instead of sensor 147, an encoder or other monitoring device on pump 143 or drive 145 may be used to provide feedback on the supply of air. A suitable power may be provided on pump 143, for example sixty horsepower. The flow of the supply of fuel may then be adjusted, for example via a gas plunger valve 139 or other suitable mechanism such as a pump, in response to the measured flow characteristic of the supply of air. In such a way the air supply is treated as a master, while the gas supply is the slave, responding to changes in the air supply. The flow of the supply of air may be adjusted up or down when the output temperature, for example detect by sensor 151, is below or above, respectively, a predetermined operating range. The controller 141 may be programmed to avoid over-correction, by making smaller incremental adjustments to air supply flow when the sensed temperature is relatively closer to a desired operating range. In some conventional burners, the burner may itself shut off entirely when a high temperature limit is surpassed, leading to potentially cold ambient air travelling through the system and causing thermal shock to previously super-heated components of the burner and fire tube.

In some cases the interior air passageways may be opened up to reduce combustion air pressure. A blower (air pump) may be used instead of a compressor a compressor may permit 1 hp/4.5 SCFM while a blower may permit 1 hp/11 SCFM, so operating cost may be reduced and capital cost reduced as well with a blower. Relatively higher air pressure may assist in creating the vacuum effect on the fuel supply line caused by air rushing past gas opening at high pressure.

During operation, the ratio of air to fuel may be controlled to produce a suitable oxygen content in exhaust gases. For example the controller may be set to produce 3-12% O2 in exhaust expelled from the burner 10. During operation, the ratio of air to fuel may be controlled to produce about 6% O2 in exhaust expelled from the burner 10. The supply of air may pass through an air pump 143 that comprises a variable frequency drive 145. A backup controller or burn management shutdown system 153 may be present to monitor operation of all components and to take over and shut down operations in the event the primary controller 141 fails.

The supply of air and the supply of fuel may be combined with the supply of air having a higher pressure than the supply of fuel. The supply of air and the supply of fuel may be combined with the supply of air having a pressure of greater than zero and below fifty, eight-five, or higher psi and the supply of fuel having a pressure of greater than zero and below twenty psi. The supply of air and the supply of fuel may be combined with the supply of air having a pressure of between nine and fifteen psi and the supply of fuel having a pressure of greater than or equal to one and less than or equal to ten psi. In some cases, the supply of air and the supply of fuel are combined with the supply of air having a pressure of about twelve psi and the supply of fuel having a pressure of about six psi. By providing a relatively higher pressure air supply, fuel from fuel-emitting outlet 114 may be relatively more efficiently drawn into flow with air ejected into mixing chamber 40 via air-emitting outlet 108.

Referring to FIG. 4, burner 10 may be connected to exhaust combusted gases through a fire tube 12 of a heat exchanger. The heat exchanger may be connected to provide heat to one or more of a frac water pond 199, a boiler, a power generator, a ground heater, a glycol vessel, a line heater, a gas dehydrator, and an oil and gas separator treater. Burner 10 may be located at an oil and gas production or processing facility. In some case a fire box application may be used instead of a fire tube.

Test Results

Example burners were tested to provide independent validation of the energy balance of the overall system, as well as document emissions reported by available instrumentation.

Test Equipment Description

System Overview

A test apparatus 14 is pictured in FIGS. 1-3. Referring to FIGS. 1-3, the apparatus 14 was enclosed in a cylindrical vessel 20 that had been insulated to minimize heat loss from external surfaces. The burner 10 fires into a 20 inch diameter U-shaped fire tube 12, allowing the burner 10 and exhaust 16 to be mounted on the same end plate. The balance of the cylindrical vessel 20 is vented to atmosphere and filled with water to cool the fire tube 12 and provide a thermal load for energy balance measurements. This cooling water stream is labelled “Process Water” and is continuously circulated at an approximately constant flow in order to maintain an acceptable internal temperature and prevent boiling. Burner nozzle cooling is achieved through the use of a water jacket to ensure the burner 10 does not overheat. This water stream is labelled “Cooling Water Jacket”, and after cooling the burner 10 it is routed into the cylindrical vessel 20 and mixed with the Process Water to assist in fire tube 12 cooling. In order to separate out the energy required for burner component cooling from the cooling load this stream applies to the fire tube 12, the energy gained is calculated at two points. The first is labelled “Cooling Jacket Water Energy Out” and indicates the energy removed by this stream from the burner components. The second is labelled “Post Burner Cooling Water Energy Out” and refers to the energy gained by this stream from cooling the fire tube 12, after it leaves the burner 10 components and enters the fire tube 12 cooling vessel. FIGS. 1 and 4, provide as-built drawings of the fire tube 12 and general apparatus layout.

An instrumentation and control system has been integrated into the apparatus 14. This system allows burner settings to be observed and controlled from a central location, while incorporating necessary protocols to ensure safe operation. Table 1 provides a summary of the instrumentation utilized for testing and analysis in this study.

TABLE 1 Summary of Instrumentation Equipment Parameter Measured Instrument Used Manufacturer Model Output Calibration Status Fuel Flow Rate

 Flow is Density Meter Micro Motion FC505113 SCFM Factory calibration 2011 Sep. 28, installed January, 2014, no calibration store installation Vessel Cooling Water Inlet Type K Thermocouple Wika TC10 deg. C. Valid calibration documents Temperature provided Vessel Cooling Water Outlet Type K Thermocouple Wika TC10 deg. C. Valid calibration documents Temperature provided Vessel Cooling Water Flow Rate Turbine Flow Meter Turbine inc. TM10G litres/coin Valid calibration documents provided Cooling Jacket Water Inlet Type K Thermocouple Wika TC10 deg. C. Valid calibration documents Temperature provided Cooling Jacket Water Flow Rate Turbine Flow Meter Turbine inc. TM150 litres/coin Valid calibration documents provided Blower Power Input True-rms Calmp Meter Fluke

 Remote Amperage Valid calibration documents Display provided Combustion Gas Analysis Flue Gas Analyzer

Temp., NO2, NCO2, Valid calibration documents ppm CO, ppm NO, provided Gross Eff., Excess Air Internal Surface Temperature IK Thermometer Fluke 52 Mini IK deg F Not calibrated Measurements Thermometer

indicates data missing or illegible when filed

Burner combustion air is provided by a turbo blower manufactured by INOVAIR™ (model: 30-100 HP), driven by an electric motor which is controlled by a variable frequency drive (VFD). Typical combustion air pressures reported by instrumentation at the burner 10 nozzle ranged from 9.4 psi-9.9 psi during the test period. Natural gas was fed to the burner 10 from utility supply, after being adjusted for pressure and flow by the PLC control. Gas pressures reported by instrumentation at the burner nozzle were steady at 2.1 psi during testing. Exhaust gas is routed through a sound suppression device (muffler 18) mounted on the side of the apparatus 14 skid and out to atmosphere.

Test Procedures

Three tests were run at approximately the same conditions and firing rate. Tests were run on three separate days with the system being powered down between testing. The system was typically started in the morning and observed until a steady state condition was indicated by constant cooling water temperatures, combustion exhaust conditions, and fuel input and control values. Time required to achieve this steadystate condition varied, due to different starting water temperatures within the cylindrical vessel 20, but was on the order of 4-6 hours due to the large volume of water contained within. During this time values reported by the command and data logging system were observed, and flue gas measurements were taken intermittently (approx. once per hour). Manufacturer instructions were followed in the operation of the flue gas analyzer.

Staff operated all command and control settings on the experimental system to ensure safety and consistent operation. In setting up the system, staff adjusted fuel flow (through PLC inputs) in order to near a targeted value of 6% O2 in the exhaust stream. These adjustments were made early in each run, with the settings then kept constant throughout the remainder of the testing.

When it was determined that the system had reached a steady-state condition, flue gas measurements were taken and printed, and a file was created containing all system values at that time, along with data from the previous 8 hours. Other information taken at steady state included electrical readings to calculate blower energy input, vessel surface temperatures, and ambient air temperatures.

Test Measurements

Energy balance measurements for the three separate runs are provided in Table 2, and emission measurements in Table 3. These values have been averaged over 2 minutes (24 data points) in order to accommodate for slight variations in values.

TABLE 2 Energy Balance Measurements Energy Balance Results Run # 1 Run # 2 Run # 3 Test Start 10:18 am   7:00 am 7:16 am Final Test Results 3:35 pm 12:35 pm 1:48 pm Test data time 3:16 pm 12:35 pm 1:36 pm Fuel Energy In [kW] 661.76 661.4 670.01 Blower Energy In [kW] 22.53 21.78 22.16 TOTAL ENERGY IN [kW] 684.29 683.18 692.17 Process Water Energy Out [kW] 334.59 331 332.69 Cooling Jacket Water Energy Out [kW] 92.14 86.87 100.34 Post-Burner Cooling Water Energy Out 157.82 155.77 141.84 [kW] Exhaust Gas Losses 126.396 128.31 127.97 Convective Heat Loss [kW] 0.741 0.251 0.192 TOTAL ENERGY OUT [kW] 711.687 702.201 703.032 Energy In − Energy Out [kW] −27.397 −19.021 −10.862 Percentage Error (From Balanced) [%] 4.0 2.8 1.6 Overall Efficiency [%] 85.4 84.0 83.1

TABLE 3 Emission Measurements Emission Measurements Run # 1 Run # 2 Run # 3 Test Start 10:18 am 7:00 am 7:16 am Final Test Results 3:35 pm 12:35 pm 1:48 pm Test data time 3:16 pm 12:35 pm 1:36 pm Exhaust Temp 261.0 deg. C. 275.1 deg. C. 273.6 deg. C. Oxygen  6.00%  5.60%  5.50% CO 0 ppm 0 ppm 0 ppm CO Air Free 0 ppm 0 ppm 0 ppm NO 27 ppm 27 ppm 25 ppm Gross Efficiency 80.90% 80.60% 80.90% Excess Air 35.80% 32.50% 31.70% CO2  8.35%  8.57%  8.63% Draft Pressure 1.598 in-H2O 1.614 in-H2O 1.698 in-H2O

Apparatus Energy Balance

In order to determine if all incoming and outgoing energy flows have been accounted for and measured properly, an overall energy balance is required. The incoming energy flow (fuel energy and blower energy) and outgoing energy flow (cooling water energy (process flow, water jacket flow, and post-burner flow), exhaust gas energy, and convective heat loss from vessel exterior) are assumed for test apparatus 14. In a steady-state condition, the energy flows will be balanced, with the incoming and outgoing energy being approximately equal (within experimental error). The system control volume in this case is taken to be the cylindrical vessel 20 enclosing the burner 10 apparatus and process cooling water.

Energy Balance Equations

${{Fuel}\mspace{14mu} {Energy}} = {{\overset{.}{V}}_{f}{{\bullet ({HHV})}\mspace{14mu}\lbrack{Watts}\rbrack}}$ Combustion  Blower  Energy = (V_(BLOWER)•A_(BLOWER))η_(MOTOR)  [Watts] ${CoolingWaterEnergy} = {{\overset{.}{m}}_{water}{\bullet C}_{Pwater}{\bullet\Delta}\; {T_{water}\mspace{14mu}\lbrack{Watts}\rbrack}}$ ${{Exhaust}\mspace{14mu} {Gas}\mspace{14mu} {Energy}} = {{\left( {{Fuel}\mspace{14mu} {Energy}\mspace{14mu} {In}} \right){{\bullet\left( {1 - {\overset{.}{Q}}_{available}} \right)}\mspace{14mu}\lbrack{Watts}\rbrack}{{Convective}\mspace{14mu} {Heat}\mspace{14mu} {Loss}}} = {\left( {{\overset{\_}{h}}_{{horiz}.{cylinder}}\pi \; {D\left( {T_{s} - T_{\infty}} \right)}\bullet \; L} \right)_{vessel} + {2{{\bullet\left( {{\overset{\_}{h}}_{{end}\mspace{14mu} {plates}}{\pi\left( \frac{D}{2} \right)}^{2}\left( {T_{s} - T_{\infty}} \right)} \right)}_{{end}\mspace{14mu} {plates}}\lbrack{Watts}\rbrack}}}}$ ${{Overall}\mspace{14mu} {Efficiency}} = {\frac{{useful}\mspace{14mu} {heat}\mspace{14mu} {output}}{{total}\mspace{14mu} {energy}\mspace{14mu} {input}} = {\frac{{{Process}\mspace{14mu} {Water}} + {{Water}\mspace{14mu} {Jacket}} + {{Post}\mspace{14mu} {Burner}\mspace{14mu} {Output}}}{{{Fuel}\mspace{14mu} {Energy}} + {{Combustion}\mspace{14mu} {Blower}\mspace{14mu} {Energy}}}\mspace{14mu}\lbrack\%\rbrack}}$ Where:                                         ${{\overset{.}{V}}_{f} = {{fuel}\mspace{14mu} {volume}\mspace{14mu} {flow}\mspace{14mu} {{rate}\left\lbrack \frac{m^{3}}{s} \right\rbrack}}}\mspace{436mu}$ ${{HHV} = {{Gross}\mspace{14mu} {Heating}\mspace{14mu} {Value}\mspace{14mu} {of}\mspace{14mu} {{Fuel}\mspace{14mu}\left\lbrack \frac{Joules}{m^{3}} \right\rbrack}}}\mspace{281mu}$ $\left( {{{actual}\mspace{14mu} {value}} = {38 \times 10^{6}\frac{Joules}{m^{3}}}} \right)\mspace{455mu}$ V_(BLOWER) = Measured  Voltage  to  Blower  Motor  [Volts]             A_(BLOWER) = Measured  Amperage  to  Blower  Motor  [Amps]           η_(MOTOR) = Stated  Efficiency  of  Blower  Motor  [%]  (actual  value = 95%) ${{\overset{.}{m}}_{water} = {{water}\mspace{14mu} {mass}\mspace{14mu} {flow}\mspace{14mu} {{rate}\mspace{14mu}\left\lbrack \frac{kg}{s} \right\rbrack}}}\mspace{400mu}$ ${C_{Pwater} = {{Specific}\mspace{14mu} {Heat}\mspace{14mu} {value}\mspace{14mu} {for}\mspace{14mu} {{water}\mspace{14mu}\left\lbrack \frac{Joules}{{{kg} \cdot \deg}\mspace{14mu} C} \right\rbrack}}}\mspace{220mu}$ Δ T = change  in  water  temperature  from  inlet  to  outlet  [deg   C]        ${{\overset{.}{Q}}_{available} = {{heat}\mspace{14mu} {available}\mspace{14mu} {to}\mspace{14mu} {system}\mspace{14mu} {due}\mspace{14mu} {to}\mspace{14mu} {fuel}\mspace{14mu} {{combustion}\mspace{14mu}\lbrack{kW}\rbrack}}}\mspace{76mu}$ ${\overset{\_}{h} = {{convection}\mspace{14mu} {heat}\mspace{14mu} {transfer}\mspace{14mu} {{coefficient}\mspace{14mu}\left\lbrack \frac{W}{{m^{2} \cdot \deg}\mspace{14mu} C} \right\rbrack}}}\mspace{211mu}$ D = vessel  diameter  [m]                               T_(s) = vessel  surface  temperature  [deg   C]                      T_(∞) = ambient  air  temperature  [deg   C]                       L = vessel  length  [m]                                

Energy Balance Results

Representative energy balance values were calculated using the equations listed above and the measured values provided in Table 2. These values are provided in Table 4. As can be seen, the error in balancing the incoming and outgoing energy flows in the system range from 4% to 1.6%. This is within expected levels of experimental error, considering the size and complexity of the system and provides confidence that the incoming and outgoing energy streams are being captured and measured correctly.

TABLE 4 Energy Balance Results Energy Balance Data Run # 1 Run # 2 Run # 3 Test Start 10:18 am 7:00 am 7:16 am Final Test Results 3:35 pm 12:35 pm 1:48 pm Test data averaged from 3:30 pm-3:32 pm 12:20 pm-12:22 pm 1:24 pm-1:26 pm Fuel Flow Rate 36.89 SCFM 36.87 SCFM 37.35 SCFM Approx. Firing Rate 2.26 MMBtu/hr 2.26 MMBtu/hr 2.29 MMBtu/hr Process Cooling Water Flow Rate 58.90 l/min 58.99 l/min 58.35 l/min Process Cooling Water Inlet Temp. 6.5 deg. C. 6.3 deg. C. 6.9 deg. C. Process Cooling Water Oulet Temp. 88.1 deg. C. 86.9 deg. C. 88.8 deg. C. Cooling Jacket Water Flow Rate 43.68 l/min 43.03 l/min 42.27 l/min Cooling Jacket Water Inlet Temp. 5.9 deg. C. 539 deg. C. 6.5 deg. C. Cooling Jacket Water Outlet Temp. 36.2 deg. C. 34.9 deg. C. 40.6 deg. C. Post-Burner Cooling Water Flow Rate 43.68 l/min 43.06 l/min 42.27 l/min (same as Cooling Jacket Flow Rate) Post-Burner Cooling Flow Inlet Temp. 36.2 deg. C. 34.9 deg. C. 40.6 deg. C. (same as Cooling Jacket Outlet Temp.) Post-Burner Cooling Flow Outlet Temp. 88.1 deg. C. 86.9 deg. C. 88.8 deg. C. (same as Process Water Outlet Temp.) Voltage to Blower Motor 480 V 491 V 481 V Amperage to Blower Motor 48.8 A 46.7 A 48.5 A Average Vessel Surface Temperature 32.5 deg. C. 29.2 deg. C. 32.6 deg. C. Average Ambient Temperature 26.5 deg. C. 26.5 deg. C. 30.4 deg. C.

DISCUSSION

As mentioned above, the level of experimental error calculated on the energy balance of the system provides confidence that all streams are being measured and represented properly. This was expected as the energy input is readily (and accurately) calculated from the fuel energy and blower energy inputs, and the majority of the outgoing energy is readily (and relatively accurately) calculated from the Process Water and Cooling Jacket Water cooling streams. The convective heat loss from the experimental apparatus is expected to have a higher degree of associated error, as the ambient air and vessel temperatures were averaged in the calculations used to determine the convective heat coefficients. The overall effect of this error is negligible however, considering that these losses are very small compared to the fuel energy rate (approx. 0.03%-0.1%).

Over the course of the three runs, Table 3 shows that the oxygen component of the exhaust air decreased. This resulted in the excess air % decreasing as the runs progressed from 1 through 3. As expected, this led to an increase in exhaust gas temperatures as well as an increase in CO2 concentration (due to lower dilution of the combustion products from excess air). Blower energy input, as a percentage of the total energy input was approximately 3.2-3.3% in all three runs.

As can be seen in Table 4, calculated values for Overall Efficiency ranged from 83.1% to 85.4%. It is interesting to note that when the Percentage Error value from each respective run is subtracted from the Overall Efficiency value, the adjusted Efficiency values range from 81.2% to 81.5%, considerably narrowing the range. Justification for subtracting the Percentage Error values from the Overall Efficiency comes from all three runs having a negative remainder when the Total Energy Out is subtracted from the Total Energy in Table 4. This indicates that in all three runs the Total Energy Out may be slightly overrepresented.

When the distribution of energy within the cooling water streams is considered, the proportion of the total system cooling load required to cool the burner 10 nozzle and associated components was found to vary from 15.1% to 17.5% during testing.

Emission measurements exhibited in Table 3 show that over the course of the three runs the burner maintained CO emissions of 0 ppm, indicating that complete combustion is likely, however It should be noted that no measurements for free hydrocarbons were taken in the exhaust stream. Low values of NO were observed over the three test runs, with values between 25-27 ppm. These results support's claims of complete, efficient combustion with low NO emissions.

Testing Preparation and Methodology

Testing on a new fire tube 12 design, in which an Inconel 800HT fire tube is tapered (“Fire tube”), beginning with an 8-inch inner diameter closest to the burner, and tapering down to a 4-inch inner diameter over 96 inches, was performed. This Fire tube design is to be incorporated in a refactory-lined chemical reactor for the gasification of solid carbonaceous material. The reactor will incorporate several Fire tubes as a method of heat addition required for gasification reactions. In such an application it is important to have consistent and controllable heat input into the reactor. The tapered Fire tube is being tested to determine if the temperature profile created along the length of the Fire tube is more consistent and uniform than a conventional fire tube.

The Fire tube was tested in conjunction with a burner 10 that incorporates a near flameless burner technology that can improve the key performance characteristics of typical combustion systems. The Absolute Extreme Burner (“AEB”) can deliver an exhaust velocity harmonic that increases the heat transfer efficiency, and the combustion efficiency, which can deliver zero Carbon Monoxide emissions, and reduced NOx emissions. The AEB Burner is capable of delivering an Exhaust Velocity Harmonic (“EVH”) that can increase heat transfer efficiency in a fire-tube application. The AEB Burner is being testing in conjunction with the Fire tube in order to determine if the EVH can create a more uniform temperature profile across the length of the Fire tube than can be expected from a conventional fire tube.

The following test protocol was agreed to by the parties prior to the commencement of testing:

Testing Protocol:

Obtain and confirm dimensions of Fire tube being shipped. Upon arrival of Fire tube, check all dimensions and surfaces for shipping damage, report same to shipper. Set up insulated test stands to anchor delivery end of the tube with AEB Burner assembly on floating 10 inch ANSI flange. Set up insulated distal test stand for keeping fire tube level and allowing for thermal expansion. Conduct first test burn to determine whether test can be continued indoors or moved outdoors.

Temperature profiles will be initially determined by direct contact measurements and thermal cameras. If the profiles meet expectations, determinations and discussions will be undertaken to decide upon further permutations and combinations of burner size, exhaust velocity, and power outputs in relation to temperature profile.

Test Facility

The Test Facility consisted of office space, as well as a warehouse area in which testing of the AEB Burner and Fire tube took place. The Fire tube was set up at the Facility along with a one million British Thermal Unit (“MMBTU”) AEB burner.

Natural gas is supplied to the Facility at an appropriate pressure for testing of the AEB Burner. An air compressor is used to compress ambient air to the pressure required for burner operation, a maximum of 30-40 psig. A water jacket was used to cool the burner assembly. The Facility was set up so that the AEB Burner and Fire tube were inside the warehouse and exhausted out of an open garage door.

Data Collection

Temperature readings were taken along the length of the Fire tube in order to determine the temperature and temperature distribution. Seven thermocouples were placed along the length of the Fire tube, with one placed closest to the burner, one placed at the end of the straight-pipe burner section, one placed at the beginning of the taper on the Fire tube, and the remaining four placed at approximately two-foot intervals along the remainder of the Fire tube.

The thermocouples were type K, ¼-inch stainless steel sheath, using standard error bands. These were used with a digital display. Data was collected during the tests by plugging the digital display into each successive thermocouple and recording the result. A minimum of three data points for each test were taken once the Fire tube reached steady state.

Approximately 220 standard cubic feet per minute (“scfm”) of combustion air is required for 1.0 MMBtu/hr of natural gas fuel. Initially, during testing the combustion air flow rate was not recorded. After several tests, it was noted that the average temperature of the Fire tube was consistently lower for the EVH runs, and ECHO personnel agreed that this was likely due to the additional combustion air required for EVH operation. This additional air would require additional heat to get it to the same temperature as the non-EVH run, therefore bringing down the average temperature of the Fire tube. After this, combustion air flow rate was recorded, but this was not until Test 11.

Testing Methodology

Tests were performed on the 8-foot Fire tube, with an 8-pitch AEB Burner and with a 14-pitch AEB Burner. These were the initial tests in which the AEB Burners were first operated with the tapered Fire tube in order to confirm they were compatible and that a consistent flame could be maintained. During these tests, a digital hand-held device was used to record temperature. Due to the varying emissivity of the Inconel 800HT, these temperature readings are not as accurate as those taken with the thermocouples, and therefore this data was not used in the analysis.

Once the operating parameters required for stable operation were established, testing commenced utilizing temperature measurements from the thermocouples. For the testing, several parameters could be adjusted, including: Burner Pitch—Two burners, 8-pitch and 14-pitch were tested. The pitch represents how many inches of burner length it would take for a revolution of the flow path. This changes the amount of “swirl” in the combustion air, and could have an effect on the heat transfer within the Fire tube; MMBTU input to burners—the AEB Burner used in the testing was rated at 1.0 MMBTU/hr. The tests were run at one of two conditions, 0.75 MMBTU/hr and 1.0 MMBTU/hr; Harmonic/Non-Harmonic operation—the AEB Burner can be operated with or without the EVH. Tests were run at both conditions; Thermocouple Insulation—the thermocouples used to record temperature along the length of the Fire tube were initially open to the ambient air. Insulation was then added to help negate the effect of ambient losses; Fire tube length and outlet diameter—the Fire tube was tested as designed (96 inches long with an outlet diameter of 4 inches) and then a length was cut from the outlet to decrease the length to 72 inches and increase the outlet diameter to 5 inches.

The test matrix below in Table 5 outlines the different tests and the associated testing parameters that were run at the Facility.

TABLE 5 TEST MATRIX Parameter Burner Fire tube Heat Length/ Input Outlet Test Burner (MMBtu/ EVH Thermocouple Diameter Number Pitch hr) Operation Insulation (in) Test 1 14-pitch  0.75 No No 96″/4″ Test 2 14-pitch  0.75 Yes No 96″/4″ Test 3 14-pitch  1.00 No No 96″/4″ Test 4 14-pitch  1.00 Yes No 96″/4″ Test 5 8-pitch 0.75 No No 96″/4″ Test 6 8-pitch 0.75 Yes No 96″/4″ Test 7 8-pitch 1.00 No No 96″/4″ Test 8 8-pitch 1.00 Yes No 96″/4″ Test 9 8-pitch 0.75 No Yes 96″/4″ Test 10 8-pitch 0.75 Yes Yes 96″/4″ Test 11 8-pitch 1.00 No Yes 96″/4″ Test 12 8-pitch 1.00 Yes Yes 96″/4″ Test 13 8-pitch 0.75 No Yes 72″/5″ Test 14 8-pitch 0.75 Yes Yes 72″/5″ Test 15 8-pitch 1.00 No Yes 72″/5″ Test 16 8-pitch 1.00 Yes Yes 72″/5″

Test Witnessing

The Fire tube testing was witnessed. Included in this was a tour of the Facility where the test setup was also inspected, including locations of temperature measurement, fuel and air introduction, the burner assembly, and ancillary equipment such as the air compressor.

Data Analysis

Temperature data was collected for each thermocouple with at least three data points for each test performed. The purpose of the testing is to determine if a more uniform temperature can be achieved across the tapered Fire tube. Thermocouple 1 and thermocouple 2 were located on the burner assembly itself and not on the Fire tube, so the data from these thermocouples were not used in the data analysis, and are included for reference only.

Additionally, during the runs in which the EVH was achieved, thermocouple 7 read significantly lower than thermocouple 6. This was not typically the case for the non-EVH tests, but was consistent across the EVH tests. It was determined that the harmonic waves produced in the Fire tube could be creating a different exhaust flow pattern during the EVH tests, which could cause ambient air to be drawn closer to the exit of the Fire tube, creating a lower exit temperature. It was agreed that further investigation into this affect was warranted, and for the purposes of these tests, thermocouple 7 would not be used.

The temperature data for each test was recorded and entered into a spreadsheet, and graphed for each test. The average temperature across the Fire tube and their standard deviation were calculated (thermocouples 3 through 6). The average temperature differential across the Fire tube (thermocouple 3 minus thermocouple 6) was also calculated. The test data from each of the tests are summarized in FIGS. 12-27, and Table 6.

It should be noted that in some cases the temperature increases at thermocouples located further down the Fire tube, meaning the temperature read closest to the burner is colder than the temperatures closer to the exit of the Fire tube. This indicates that some of the thermocouples may have been reading high or low during the testing. The thermocouples were not changed during the course of the testing, and if one or more of the thermocouples were reading high or low, this should have continued throughout the testing. Therefore, while the actual temperature read may not be accurate, the changes in these temperatures should be consistent. The results of the testing are based on average temperatures and temperature differentials across the different tests, therefore the results are still valid.

TABLE 6 Test Data Temp. Standard Average Differential Deviation Temp (F.) (F.) (F.) TC3-TC6 TC3-TC6 TC3-TC6 Test 1 - 0.75 MMBtu; No EVH 811.6 32.4 33.2 Test 2 - 0.75 MMBtu; EVH 941.7 (1.3) 25.9 Test 3 - 1.0 MMBtu; No EVH 1,031.7 (31.3) 21.9 Test 4 - 1.0 MMBtu; EVH 997.1 (35.4) 25.9 Test 5 - 0.75 MMBtu; No EVH 982.2 10.8 23.5 Test 6 - 0.75 MMBtu; EVH 917.3 (16.7) 12.2 Test 7 - 1.0 MMBtu; No EVH 1,017.9 (53.4) 29.0 Test 8 - 1.0 MMBtu; EVH 985.0 (49.9) 30.5 Test 9 - 0.75 MMBtu; No EVH 1,331.5 163.5 73.8 Test 10 - 0.75 MMBtu; EVH 1,217.7 96.6 44.7 Test 11 - 1.0 MMBtu; No EVH 1,351.4 94.5 43.8 Test 12 - 1.0 MMBtu; EVH 1,306.7 82.1 41.1 Test 13 - 0.75 MMBtu; No EVH 1,311.7 177.7 77.3 Test 14 - 0.75 MMBtu; EVH 1,205.2 147.9 61.2 Test 15 - 1.0 MMBtu; No EVH 1,338.6 118.4 50.3 Test 16 - 1.0 MMBtu; EVH 1,292.2 112.4 46.7

From the data presented above, the following general conclusions can be made: The average temperature of the Fire tube decreases as EVH is introduced. This is a result of the increased combustion air required to achieve EVH. The additional combustion air is introduced at near-ambient conditions, and therefore must be heated by the energy released during combustion of the fuel. In order to correct for this effect, the heat lost to the combustion air must be modeled (see below). The temperature differential across the Fire tube (from thermocouple 3 to thermocouple 6) generally decreases when EVH is introduced. The average temperature differential for all tests without EVH is 69 degrees F., and with EVH it is 42 degrees F. This indicates that the EVH may lead to more uniform temperatures across the Fire tube. The standard deviation of all temperatures across the Fire tube (from thermocouple 3 to thermocouple 6) generally decreases when EVH is introduced. The average standard deviation for all tests without EVH is 46 degrees F., and with EVH it is 36 degrees F. This indicates that the EVH may lead to more uniform temperatures across the Fire tube. It should be noted that the change in standard deviation due to EVH was measured only at the 0.75 MMBtu/hr case (52 F vs 36 F), and for the 1.0 MMBTU/hr case there was no change (36 F vs 36 F). The 14-pitch and 8-pitch runs did not appear to have any discernable, repeatable differences in temperature profiles. For the 0.75 MMBtu runs, the 8-pitch provided lower standard deviations, and lower temperature differentials, however for the 1.0 MMBtu runs, the 8 pitch provided similar temperature differentials and standard deviations. (It should be noted that for the 0.075 MMBtu, no EVH runs, the 8 pitch shows a significantly higher average temperature than the 14-pitch run. The data suggests that for the 14 pitch run, the Fire tube may have not reached steady state, and therefore the temperature may be lower than expected.) The outlet diameter and length of the Fire tube had significant effects on the temperature differentials and standard deviation of the temperatures. The change from 4-inch outlet diameter to 5-inch outlet diameter would theoretically decrease the pressure differential across the Fire tube (based on model results, the change in differential pressure would be approximately 0.1 psi). With a lower pressure differential, one would expect a higher temperature differentials, and a less uniform temperature distribution. When the outlet diameter was increased, in each case, the temperature differential increased, and the standard deviation decreased. This indicates that inducing a pressure differential across the Fire tube does lead to a more uniform temperature distribution along the Fire tube.

Data Matching and Modeling

A process model was developed using the software VMGSim (“VMG Model”) to model the burner and Fire tube test setup, and verify results. Included in the VMG Model are fuel and combustion air inputs, heat transfer coefficients and heat loss calculations for each of the tests performed. The purpose of this model is to determine the effect of the additional combustion air required for the EVH, so that this can be quantified. Once quantified, a match can be made from the test data, in order to determine the increase in efficiency (heat transfer coefficients) of the EVH vs non-EVH runs. Additionally, the VMG Model results will be compared to the modeled results of a straight (non-tapered) fire tube, so that the efficiency gains in heat transfer due to the tapered Fire tube and therefore increased back pressure can be estimated.

Recommendations

The following recommendations are based on the test results discussed above: Continue modelling efforts to better understand the effect of combustion air on the temperature profiles and heat transfer coefficients. Repeat the above tests using a straight (non-tapered) fire tube in order to provide a control for the experiment. Investigate more cost effective ways to produce the same effect in the Fire tube. If the efficiency gains and more uniform temperature profiles seen in the tests are a result of back pressure on the fire tube, it is possible a straight fire tube with an orifice at the exhaust end would work as well. This would offer two benefits: 1) much lower manufacturing costs (straight fire tube vs tapered) and 2) better heat transfer areas (as the tube tapers, the diameter decreases and the heat transfer area decreases with the square of the diameter; a 50% decrease in diameter from 8″ to 4″ leads to a 75% decrease in heat transfer area from 50″ to 12″). Explore options for further testing in order to get more accurate, repeatable temperature profiles, and to collect more data, including: pressure differentials, continuous metering of natural gas and combustion air, etc. This could help define the changes induced by the EVH, and could help to understand and optimize the benefits thereof.

The fire tube 12 may have a plurality of sensors comprising bottom sensors and top sensors (15 b).

TABLE 7 Cross-sectional areas of one set of examples air outlets 108 AREA CALCULATOR Mixing Chamber Output (Nozzle to combustion chamber housing) AREA SEGMENT Combined area for five Diameter (for each outlet 108) vanes (six outlets 108) REF. 4″ 5 VANES- 0.86230016 4.3115 INPUTS 3″ DIA. INPUTS 0.48504384 2.42522 (SCALED) 2″ DIA INPUTS 0.21557504 1.07788 (SCALED) 1″ DIA. INPUTS 0.05389376 0.26947 (SCALED) CUSTOM DIA. INPUTS 1.34734399 6.73672 (SCALED)

TABLE 8 Cross-sectional areas of a second set of examples air outlets 108 AREA CALCULATOR Mixing Chamber Output (Nozzle to combustion chamber housing) AREA SEGMENT Combined area for five Diameter (for each outlet 108) vanes (six outlets 108) REF. 4″ 5 VANES-. 0.36528678 1.82643 INPUTS 3″ DIA. INPUTS 0.20547381 1.02737 (SCALED) 2″ DIA. INPUTS 0.09132169 0.45661 (SCALED) 1″ DIA. INPUTS 0.02283042 0.11415 (SCALED) CUSTOM DIA. INPUTS 0.57076059 2.8538 (SCALED)

TABLE 9 Cross-sectional areas of second nozzles/fuel-emitting outlets 114 Mixing Chamber SINGLE JET Output (Nozzle to BORE (fuel-emitting combustion (passageway) outlet 114) COMBINED chamber housing) 112 AREA (A AREA (B in AREA OF SIX Diameter in FIG. 8B) FIG. 8B) JETS REF. 4″ 5 VANES-. 0.78539816 0.19634954 1.17809725 INPUTS 3″ DIA. INPUTS 0.44178647 0.11044662 0.6626797 (SCALED) 2″ DIA. INPUTS 0.19634954 0.04908739 0.29452431 (SCALED) 1″ DIA. INPUTS 0.04908739 0.01227185 0.07363108 (SCALED) CUSTOM DIA. 1.76714587 0.44178647 2.6507188 INPUTS (SCALED)

TABLE 10 Comparison of fuel and air nozzle cross-sectional areas Nozzle max min min diameter air SA air SA fuel SA max air/fuel SA air/fuel SA 4 4.3 1.8 1.2 3.583333333 1.5 3 2.4 1 0.7 3.428571429 1.428571429 2 1.1 0.5 0.3 3.666666667 1.666666667 1 0.3 0.1 0.1 3 1

TABLE 11 Dimensions of combustion chamber housings for different sample burner sizes COMBUSTION BURNER SIZE CHAMBER W/ (Mixing chamber USABLE outlet 132/nozzle HARMONICS diameter) AREA LENGTH VOLUME 3½″ ID (1st 1″ NOZZLE 9.62 16 154 EVH) 6¾″ ID (2nd 2″ NOZZLE 35.8 23 823 EVH) 10 5/16″ OD (2nd 3″/4″ NOZZLE   85.5 25 2138 EVH)

TABLE 12 sample run data for a burner Minimum fire run 0.7 MMBTU/H Manifold = 0.5 psi Combustion air flow 3.62 0.27 (differential pressure in inches of water) Gas flow in SCFM 57.39 11.77 Gas flow in SCFH 3443 705.9 VFD Speed PSI/Temp 757.5 163.6 Compensated to SCFM VFD speed FB (%) 100.1 29.8 Combustion air pressure (psi) 10.3 .8 Combustion air temperature (C.) 79.1 27.1 Cooling Jacket Temperature (C.) 50.5 20.1

In the claims, the word “comprising” is used in its inclusive sense and does not exclude other elements being present. The indefinite articles “a” and “an” before a claim feature do not exclude more than one of the feature being present. Each one of the individual features described here may be used in one or more embodiments and is not, by virtue only of being described here, to be construed as essential to all embodiments as defined by the claims. 

1-54. (canceled)
 55. A method comprising: supplying a flow of fuel and oxygen to a combustion chamber housing of a burner; and igniting the flow of fuel and oxygen within the combustion chamber housing using an igniter located within a pilot chamber that opens into the combustion chamber housing.
 56. A burner comprising: a fuel supply line; an oxygen supply line; a combustion chamber housing connected to receive a flow of fuel and oxygen from the fuel supply line and the oxygen supply line; and an igniter located within a pilot chamber that opens into the combustion chamber housing. 57-62. (canceled) 